228W Poster - Population Genetics
Wednesday June 08, 8:30 PM - 9:15 PM

Authors:
Yocelyn Gutierrez-Guerrero ¹; Megan Phifer-Rixley ²; Felipe Martins ^1,3; Michael W Nachman ¹

Affiliations:
1) Museum of Vertebrate Zoology, Department of Integrative Biology, University of California Berkeley, Berkeley, CA, US; 2) Department of Biology, Monmouth University, West Long Branch, New Jersey, US; 3) Department of Ecology and Evolution, The Australian National University Acton, Canberra, Australia

Keywords:
Natural selection

Parallel evolution in response to similar selection pressures can provide strong evidence of natural selection. For example, Drosophila melanogaster shows phenotypic and genotypic clines in opposite directions in the northern and southern hemispheres. House mice (Mus musculus domesticus) also provide an excellent opportunity for studying the genetic basis of how species adapt to new environments. Native to Europe, they have been spread around the world in the association with humans in the last few hundred years. Previous studies of house mice from latitudinal transects in eastern and western of North America identified phenotypes and genes that underlie environmental adaptation, including differences in body size and signatures of parallel evolution in genes involved in thermoregulation. Here, we expand the geographic scale to include a latitudinal transect across South America with the aim of identifying unique and shared responses to selection in the northern and southern hemispheres. We sequenced the complete exomes of 76 wild-caught mice spanning 50 degrees of latitude across Brazil and Argentina. Principal components analysis revealed a clear separation between populations from North and South America. Using a Latent Factor Mixed Model (LFMM Ridges), we conducted genome-wide scans for selection by looking for associations between genotypes and environmental variables separately in North and South America. We detected thousands of SNPs significantly associated with latitude, annual mean temperature, and temperature seasonality (q-value≤ 0.001 and zscore≥ 2). In the populations from South America, we identified candidate genes involved in lipid metabolism, circadian rhythm, morphogenesis, and regulation of cold thermogenesis. To explore parallel evolution in the northern and southern hemispheres, we identified the subset of genes showing significant associations in each transect. Permutation tests revealed more overlap than expected by chance (pvalue≤ 0.001). Of particular note is the discovery that the genes underlying cold and heat sensation (Trpm8 and Trpm2) show clear signatures of selection in both hemispheres. Since mice independently colonized North and South America, these results suggest repeatable evolution driven by adaptation to thermal conditions. Moreover, newly developed wild-derived inbred strains of mice from different latitudes provide opportunities for functional tests of alternative alleles at Trpm8 and Trpm2 in the laboratory.